Within the general field of barrel-type engines, there exist two primary classes of engines: swashplate barrel engines and camplate barrel engines. The two classes of barrel engines can be distinguished by the properties of the drive mechanisms they employ to convert the reciprocating motion of the pistons into rotational motion of the driveshaft.
Swashplate barrel engines utilize a drive means that consists of an angled plate capable reciprocating the pistons through two cycles per one revolution of the driveshaft. A piston in a swashplate barrel engine generally communicates with the swashplate via a slipper pad in sliding contact with the surface of the swashplate or with a universal type joint attached to an annular ring in sliding contact with the surface of the swashplate. An example of a swashplate barrel engine is illustrated in FIG. 12.
Cam plate barrel engines utilize a drive means that consists of a plate with an undulating cam surface normally capable of reciprocating the pistons through four or more cycles per one revolution of the driveshaft. A piston in a swashplate barrel engine generally communicates with the camplate via a pair of rolling elements that follow the undulating surface of the camplate.
In both swash plate barrel engines and camplate barrel engines, high side loads exist at the point where the pistons communicate with the angled surfaces of the swashplate or camplate. This side loading must be reacted somewhere within the piston apparatus without generating unacceptably high levels of friction and wear.
In the field of camplate barrel engines, very little progress has been made to reduce the friction forces that result from side loading within the piston apparatus. As a result, the friction generated in camplate barrel engines can be as much as 70% higher than a conventional crankshaft driven engine, having a negative impact on fuel economy and limiting the adoption of these engines. Several attempts have been made to isolate side loads from the piston skirts in camplate barrel engines. Various versions of guide rod strategies have been proposed. However, to date, there has yet to be a structurally viable example of a guide rod/piston assembly in a camplate barrel engine.
One design that seeks to address the side loading issue is shown in U.S. Pat. No. 5,771,694, which is illustrated in FIGS. 13A and 13B. The '694 reference discloses a double guide rod mechanism which guides the piston during its reciprocating motion in the cylinder. The side loads are generally carried by the guide rods at the swashplate interface instead of the piston skirts, thereby resulting in an overall reduction in friction and increased engine efficiency over an unguided system. However,
FIG. 14 illustrates another double guide rod apparatus as proposed in U.S. Pat. No. 4,553,508 to Stinebaugh. In this design, the attachment of the camplate rollers to the piston apparatus will not survive under normal engine operation. At as low as 3000 RPM, the inertial forces transferred through the roller pins in camplate barrel engines are on the order of 12,000 to 15,000 pounds. Under these forces, a camplate roller pin supported on only one end will break.
FIG. 15 illustrates another guide rod apparatus as proposed in U.S. Pat. No. 1,063,456 to Looney. In this design, only one guide rod is used to handle side loads from the piston apparatus. To prevent rotation of the piston apparatus, an extension is provided on the backside of the guide rod bearing which slides within a track in the engine block. Similar to the design proposed in U.S. Pat. No. 4,553,508, the cam plate roller pins are only supported on one end. This design as shown will not withstand the conditions associated with normal engine operation.
FIG. 16 illustrates a square guide apparatus as proposed in U.S. Pat. No. 5,566,578 to Rose. In this design, the piston apparatus itself slides within a square slot that receives the side loads from the camplate rollers. This design is also flawed because the camplate rollers are supported on only one end.
FIG. 17 illustrates an additional style of guide apparatus as proposed in PCT/BG97/00005 to Bahnev that includes slots in the piston apparatus. The slots in the piston apparatus engage linear bearings attached to the block. This design also uses camplate rollers with the pin supported on one end and will also fail under normal engine operation.
Thus, FIGS. 13-17 illustrate guide rod mechanisms that have been proposed. It will be evident to one who is skilled in the art that none of these mechanisms will survive within the operating environment of an internal combustion engine. Therefore, it remains desirable to provide an improved guide system that overcomes the inherent weaknesses of conventional guide systems.